Tophen was a metropolitan area located on the Outer Rim Territories world of Christophsis. As the Imperial Era approached, it became the home of the prime minister governing the planet. With the minister's guidance, Tophen started functioning as a central hub for the Christophsis insurgents, a resistance movement against the Galactic Empire.
The prime minister faced execution in 3 BBY due to treason against the Empire, following a wave of arrests after the Empire learned of his connection to Tophen's rebel forces. Subsequently, the Empire "pacified" Tophen for its role as a focal point of insurgent actions. Grand Moff Wilhuff Tarkin revealed Tophen's destiny in a speech to the Imperial Senate, presenting it as a triumph for the Empire's future.
Leia, Princess of Alderaan, a young-adult novel from 2017 penned by Claudia Gray, featured a reference to Tophen.